Field
Embodiments described herein generally relate to a method and apparatus for encapsulating an organic light emitting diode (OLED) structure, more particularly, to a thin film encapsulation (TFE) structure for an OLED structure.
Description of the Related Art
Organic light emitting diode displays (OLED) have gained significant interest recently in display applications in view of their faster response times, larger viewing angles, higher contrast, lighter weight, lower power and amenability to flexible substrates. Generally, a conventional OLED is enabled by using one or more layers of organic materials sandwiched between two electrodes for emitting light. The one or more layers of organic materials include one layer capable of monopolar (hole) transport and another layer for electroluminescence and thus lower the required operating voltage for OLED display.
In addition to organic materials used in OLED, many polymer materials are also developed for small molecule, flexible organic light emitting diode (FOLED) and polymer light emitting diode (PLED) displays. Many of these organic and polymer materials are flexible for the fabrication of complex, multi-layer devices on a range of substrates, making them ideal for various transparent multi-color display applications, such as thin flat panel display (FPD), electrically pumped organic laser, and organic optical amplifier.
OLED structures may have a limited lifetime, characterized by a decrease in electroluminescence efficiency and an increase in drive voltage. A main reason for the degradation of OLED structures is the formation of non-emissive dark spots due to moisture or oxygen ingress. For this reason, OLED structures are typically encapsulated by a buffer layer sandwiched between barrier layers. The buffer layer is utilized to fill any voids or defects in the first barrier layer such that the second barrier layer has a substantially uniform surface for deposition. The buffer layer and the barrier layers may be fabricated from different materials including organic materials or inorganic materials as needed for different moisture resistance, film optical transparency and process requirements. However, different materials, especially organic and inorganic materials, often have different film properties, thereby resulting in poor surface adhesion at the interface where the organic and the inorganic layers are in contact with. Poor interface adhesion often allows film peeling or particle generation, thereby adversely contaminating the device structure and eventually leading to device failure. Additionally, poor adhesion at the interfaces between the organic and inorganic materials may also increase the likelihood of film cracking, thereby allowing the moisture or air to sneak into the device structure, thereby deteriorating the device electrical performance.
Therefore, an improved method and apparatus for encapsulating an OLED structure is needed.